#include<iostream>
using namespace std;
class Circle{
	private:
		double radius;
	public:
		Circle(double r) : radius(r){}
	friend double calculateArea(Circle c);
		
};
double calculateArea(Circle c){
	return 3.14 * c.radius * c.radius;
}
int main()
{
	Circle circle(5);
	std::cout<<"Area: "<<calculateArea(circle)<<std::endl;
	return 0;
}